JS Type Extender (inspired by backbone.js)

extender.js

//IE9+
(function () {
    "use strict";

    function merge(){ //shallow copy
        var root = arguments[0], fromObj;
        
        for (var i = 1; i < arguments.length; i++) {
            fromObj = arguments[i];

            Object.keys(fromObj).forEach(function(pName){
                root[pName] = fromObj[pName];                 
            });
        }

        return root;
    }

    return function extenderAttachFn(typeToExtend, inheritExtend) {

        typeToExtend.extend = function extend(props) {
 
            var constructor = (props.hasOwnProperty("constructor") ? props.constructor : typeToExtend ); //allow the extending props to define its own constructor method
 
            var newType = function(){
                constructor.apply(this, arguments); //only now we call the parent constructor function
            };
 
            newType.prototype = merge(Object.create(typeToExtend.prototype), props); //using Object.create we create an object out of the parent prototype without calling the constructor function
 
            if (inheritExtend){ //make the extended type also extendable and so on and so on
                extenderAttachFn(newType, true);
            }
 
            newType.create = _create.bind(null, constructor, newType.prototype);//allow creating a new instance without the need for New keyword
 
            return newType;
        }
    };
    
    function _create(constructor, proto){
        var instance = Object.create(proto);
        var args = Array.prototype.splice.call(arguments, 2);
        constructor.apply(instance, args);
        return instance;
    }
})();

extenderExample.js

function A(options){
    this.name = options.name();
}

A.prototype.doSomething= function(){
    console.log("A");
}

extenderAttachFn(A, true);

var B = A.extend({
   showName: function(){
       console.log("my name = " + this.name);
   } 
});

B.prototype.doSomething= function(){
    console.log("B");
}

 var C = A.extend({
   showName: function(){
       console.log("I am " + this.name);
   } 
});

C.prototype.doSomething= function(){
    console.log("C");
}

var D = B.extend({
   showName: function(){
       console.log("mi nombre " + this.name);
   } 
});

D.prototype.doSomething= function(){
    console.log("D");
}

var b = new B({name: function(){return "moshe";}});
var b2 = new B({name: function(){return "haim";}});

b.showName();
b.doSomething();
b2.showName();

var c = new C({name: function(){return "James";}});
c.showName();
c.doSomething();

var d = new D({name: function(){return "Angel";}});
var d2 = new D({name: function(){return "Jesus";}});

d.showName();
d.doSomething();
d2.showName();

console.log("b instanceof A = ", b instanceof A);
console.log("b instanceof B = ", b instanceof B);

console.log("c instanceof A = ", c instanceof A);
console.log("c instanceof B = ", c instanceof B);

console.log("d instanceof A = ", d instanceof A);
console.log("d instanceof B = ", d instanceof B);
console.log("d instanceof C = ", d instanceof C);

console.log("d2 instanceof A = ", d2 instanceof A);
console.log("d2 instanceof B = ", d2 instanceof B);
console.log("d2 instanceof C = ", d2 instanceof C);